Why is it that sometimes we're just "not in the mood?" That one may feel "up" one day and "down" the next is a facet of life experienced by almost all men and women at least since the beginning of recorded time. People have looked to psychology, biology, astrology, numerology, and various other disciplines, including Biorythms, to try to make sense (and to predict) humankind's constantly changing moods and dispositions.

As far as we know, modern Biorhythms date back to somewhere around the end of the 19th century,when Dr. Hermann Swoboda, a professor of psychology at the University of Vienna, began to ponder these dispositional changes and sought to chart some sort of regularity and predictability therein. Out of his early research (1897-1902) came his discovery of two basic rhythms in humans which he considered to be certain.These two cycles were a 23 day cycle and a 28 day cycle.He assigned a "masculine" quality to the 23 day cycle(hence physical influence) and a "feminine" quality to the 28 day cycle (i.e., emotional influence).